1. Field of the Invention.
This invention relates generally to earth materials and the environment. More specifically, this invention relates to a process for treating rock heaps to prevent oxidized species release, including acid drainage, therefrom.
2. Related Art.
Acid drainage from closed mines and waste heaps has been an important environmental problem. Prior art methods to alleviate this problem include collecting and treating acidic water discharged from the polluting source. Also, other treatment methods have attempted to prevent the acid drainage from the source in the first place.
U.S. Pat. No. 4,861,482, issued Aug. 29, 1989, (Frankenberger et al) discloses removing selenium from soil and water by adding nutrients, including cobalt, zinc and nickel ions, for microbes in the soil or water, resulting in the formation of volatile alkylselenides.
U.S. Pat. No. 5,387,271, issued Feb. 7, 1995, (Crawford et al) discloses biodegrading nitroaromatics in soil and water with a first fermentation operation performed by an inoculum of aerobic and/or facultative microorganisms fed by an added carbohydrate nutrient. This first operation is followed by a second anaerobic operation performed by an inoculum of mixed anaerobic microorganisms fed by the remaining carbohydrate nutrient.
U.S. Pat. No. 5,399,048 (Walker), issued Mar. 21, 1995, discloses capping an exposed rock heap surface with an impermeable coating containing seeds and/or a coloring additive for esthetic purposes.
U.S. Pat. No. 5,616,251 (Batarseh), issued Apr. 1, 1997, discloses treating material causing acid mine drainage with a liquid containing a Lewis base group (M--) attached to a hydrophobic group (--R) for example, water-soluble alkylated phosphate. The Lewis base group component reacts with the metal in the acid-causing material.
U.S. Pat. No. 5,632,715 & 5,710,361 (Harrington et al.), issued May. 27, 1997 and Jan. 20, 1998, respectively, disclose in-situ immobilization of metals in waste heaps by injecting a nutrient into a passageway into the heap, the nutrient feeding sulfide-producing microorganisms also provided to the heap to create less-soluble metal sulfides in the heap.
Still, there exists a need to prevent acid drainage from rock heaps indefinitely in a self-sustaining manner. This invention addresses that need.